[Kitten (OP)]

Can anyone who understands physics/acoustics explain to me why pianos and harps have that particular curved shape? I am a harpist and forever being asked this, but because I'm a biologist with an aversion to maths and physics, I haven't got a clue.
Thanks! And happy new year!

"I have not failed, I have merely found ten thousand ways which do not work"

[Ylide]

I believe it has something to do with the strings needing to be different lengths to resonate at different frequencies.  The reason for that exact shape I cannot say, but you'll note that the lengths of the strings of your harp are longer at one end than at the other.  (and different diameter/material as well)  



This message brought to you by The Council of People Who Are Sick of Seeing More People

[mawea]

I can only think of 2 reasons , 1st one has been explained - the shape is to produce different tones when different stings are striked , 2nd reason is to have a shape strong enough to keep the whole structure intact , considering the total amount of force produced from the tight tension strings or metal wires. If the structure somehow changes , the instrument will be off key.

[tweener]

Yes, you notice that each string is a little different length than the others.  The shorter strings make a higher pitched note.  The longer strings are made from thicker material so that they will vibrate at an even lower frequency (thus a lower note).  If you look at the shape of a grand piano, you see the same sort of arched shape, only on its side, for exactly the same reason.

The shape of the instrument also plays a major role in the "timbre" of the sound.  The timbre is the characteristics of the vibration that makes a harp sound different from a piano or violin, even though they are playing the same note.  The resonance of the instrument makes the unique sound for that instrument.

As for the detailed mathematical and physical analysis, it is well understood why strings of different lengths, tension and material make different fundamental sound.  However, I don't think anyone really understands exactly why a Stradivarius violin sounds different from a well made imitation.


----
John